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Ash/Tephra Fall

Geologists examining ash layers associated with the Dusty assemblag...
Geologists examining ash layers associated with the Dusty assemblage, deposited between 5,000 and 7,000 years ago. Glacier Peak, Washington.  (Credit: Bleick, Heather. Public domain.)

Both of the large Plinian-style eruptions of Glacier Peak released many times more tephra than the May 18, 1980 eruption of Mount St. Helens. Such large tephra eruptions would have widespread effects and could deposit enough material to collapse roofs in the nearby downwind communities. Owing to prevailing wind patterns, tephra fall during future eruptions is most likely east of Glacier Peak, but it could affect communities in all directions from the volcano depending upon wind patterns during an eruption.

In areas downwind from Glacier Peak, even small tephra eruptions could disrupt air and ground transportation and dust towns with ash. Tephra could clog drainage ducts and ventilation filters, short- circuit power transformers, damage machinery and electronic equipment, reduce visibility, exacerbate respiratory ailments, and stall transportation. Damage from tephra can be mitigated by such actions as shutting down and covering equipment, frequently replacing air filters in machinery, wearing dust masks, and avoiding unnecessary travel. To learn more about ash fall, visit the volcanic ash website.